Illumination light projection for a depth camera

ABSTRACT

Various embodiments of TOF depth cameras and methods for illuminating image environments with illumination light are provided herein. In one example, a TOF depth camera configured to collect image data from an image environment illuminated by illumination light includes a light source including a plurality of surface-emitting lasers configured to generate coherent light. The example TOF camera also includes an optical assembly configured to transmit light from the plurality of surface-emitting lasers to the image environment and an image sensor configured to detect at least a portion of return light reflected from the image environment.

BACKGROUND

In a time-of-flight (TOF) depth camera, light pulses are projected froma light source to an object in an image environment that is focused ontoan image sensor. It can be difficult to fill the image environment withillumination light, as the image environment may have a sizeable volumeand may have a cross-sectional shape (e.g. rectangular) that can bedifficult to achieve with a desired intensity profile. Further, theimaging optics may have a large depth of field in which a consistentprojected light intensity is desired.

Some previous approaches to filling image environments with light usehigh-order optics to shape diverging light emitted from side-emittinglight sources. However, such approaches typically require precise designand manufacturing control of the angular distribution of the light inorder to fill the image environment.

SUMMARY

Various embodiments related to illuminating image environments withillumination light for a TOF depth camera are provided herein. Forexample, one embodiment provides a TOF depth camera configured tocollect image data from an image environment illuminated by illuminationlight is provided. The TOF camera includes a light source including aplurality of surface-emitting lasers configured to generate coherentlight. The TOF camera also includes an optical assembly configured totransmit light from the plurality of surface-emitting lasers to theimage environment and an image sensor configured to detect at least aportion of return light reflected from the image environment.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. Furthermore,the claimed subject matter is not limited to implementations that solveany or all disadvantages noted in any part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows an example time-of-flight (TOF) depth camerain an example use environment according to an embodiment of the presentdisclosure.

FIG. 2 schematically shows an example light source according to anembodiment of the present disclosure.

FIG. 3 schematically shows an example surface-emitting laser accordingto an embodiment of the present disclosure.

FIG. 4 schematically shows another example surface-emitting laseraccording to an embodiment of the present disclosure.

FIG. 5 shows an example illumination profile according to an embodimentof the present disclosure.

FIG. 6 schematically shows an example lens system according to anembodiment of the present disclosure.

FIG. 7 schematically shows another example lens system according to anembodiment of the present disclosure.

FIG. 8 schematically shows another example lens system according to anembodiment of the present disclosure.

FIG. 9 schematically shows an example homogenizing light guide accordingto an embodiment of the present disclosure.

FIG. 10 schematically shows a portion of an example microlens arrayaccording to an embodiment of the present disclosure.

FIG. 11 schematically shows a perspective view of an example lenselement in a microlens array according to an embodiment of the presentdisclosure.

FIG. 12 schematically shows another example homogenizing light guideaccording to an embodiment of the present disclosure.

FIG. 13 schematically shows an example reflective light guide accordingto an embodiment of the present disclosure.

FIG. 14 shows a flowchart illustrating an example method of projectingillumination light into an image environment according to an embodimentof the present disclosure.

DETAILED DESCRIPTION

As mentioned above, a TOF depth camera utilizes light pulses (e.g.infrared and/or visible light) projected from the TOF depth camera intoan image environment. The illumination light pulses reflect from thevarious surfaces of objects in the image environment and are returned toan image sensor. The TOF depth camera generates distance data byquantifying time-dependent return light information. In other words,because light is detected sooner when reflected from a feature nearer tothe photosensitive surface than from an object feature farther away, theTOF depth camera can determine distance information about the object'sfeatures.

It may be difficult to fill the image environment with illuminationlight of a desired intensity profile. For example, it may be desirablefor the intensity of the project light to be somewhat greater in aregion near a periphery of the image environment than in a center of theimaging environment, as light reflected from those regions may have alower intensity at the image sensor due to the angle of incidence on theimaging optics.

Further, as mentioned above, the imaging environment may have adifferent cross-sectional shape than light emitted by the light source.The imaging environment also may be relatively large to capturepotentially large ranges of movements of potentially multiple users.

Illumination sources used with TOF depth cameras may emit light incircular patterns or circularly-shaped emission envelopes. Therefore,overlaying a circularly-shaped emission pattern onto a non-circularimage environment in a manner that achieves a relatively uniformillumination intensity across the entire non-circular image environmentmay result in the illumination of portions of the environment that arenot used for depth analysis. This may waste light source power, and alsomay involve the use of a more powerful and expensive light source.

Some previous approaches to reshaping illumination light employ randomdistributions of spherical microlenses. By randomly distributing themicrolenses, the shape of the emitted light may be adjusted whileavoiding the introduction of diffractive interference that may resultfrom a periodic arrangement of microlenses. However, because themicrolenses are randomly sized, the ability to control the distributionof light within the image environment, including the light'scross-sectional profile and the dimensions of the envelope that itilluminates within the room, may be compromised.

Accordingly, various embodiments of TOF depth cameras and methods forilluminating image environments with illumination light are providedherein. For example, in some embodiments, a TOF depth camera includes alight source including a plurality of surface-emitting lasers configuredto generate coherent light. The example TOF camera also includes anoptical assembly configured to transmit light from the plurality ofsurface-emitting lasers to the image environment and an image sensorconfigured to detect at least a portion of return light reflected fromthe image environment. The plurality of surface-emitting lasers may bearranged in a desired illumination light shape, thereby allowing animage of the shape of the light source to be relayed into the imageenvironment. In other embodiments, a homogenizing light guide may beconfigured to provide a shaped light source for such use.

FIG. 1 schematically shows an embodiment of a TOF depth camera 100. Inthe embodiment shown in FIG. 1, TOF depth camera 100 includes anilluminator 102 configured to illuminate a portion of an object 104positioned in an image environment 106 with illumination light 108. Forexample, a ray of illumination light 108A striking a portion of object104 is reflected as return light 112. Photons from return light 112 maybe collected and used to generate depth information for object 104, asexplained in detail below.

While the example shown in FIG. 1 depicts a single illuminator 102included within TOF depth camera 100, it will be appreciated that aplurality of illuminators 102 may be included within TOF depth camera100 to illuminate an image environment.

TOF depth camera 100 also includes an image sensor 110 configured todetect at least a portion of return light 112 reflected from imageenvironment 106. Image sensor 110 includes a detector 114 for collectingreturn light 112 for use in generating depth information (such as adepth map) for the scene.

In the embodiment shown in FIG. 1, illuminator 102 includes a lightsource 118 configured to generate coherent light and an optical assembly120 configured to shape the coherent light and direct it toward imageenvironment 106. Light source 118 may emit coherent light at anysuitable wavelength(s), including but not limited to infrared andvisible wavelengths.

FIG. 2 schematically shows an embodiment of light source 118 including alaser array 200 comprising a plurality of individual surface-emittinglasers 202. It will be appreciated that laser array 200 may have anysuitable shape without departing from the scope of the presentdisclosure. In the embodiment shown in FIG. 2, laser array 200 has arectangular/oblong shape, which matches a desired illumination lightcross-sectional shape. It will be appreciated that a plurality ofsurface-emitting lasers 202 may have any other suitable shape and/orpattern.

Surface-emitting lasers 202 may be fabricated on a suitable substrate(e.g., GaAs) using large-scale integration techniques (e.g., filmdeposition and film patterning techniques). In some examples, a diecomprising a laser array 200 may include hundreds or more ofsurface-emitting lasers 202. For example, a 1.5 mm square die includingsurface-emitting lasers 202 that have a center-to-center pitch ofapproximately 44 μm may include up to 1156 surface-emitting lasers 202.

FIG. 3 schematically shows a cross-sectional view of an embodiment of asurface-emitting laser 202. Specifically, the embodiment ofsurface-emitting laser 202 shown in FIG. 3 is a vertical-cavitysurface-emitting laser (VCSEL). A VCSEL is a semiconductor laser diodethat emits laser light perpendicular from a substrate surface on whichthe VCSEL is formed. Light or current is pumped into the VCSEL via apump source to excite the active laser medium (e.g., the material suitedto stimulated emission in response to the pump source—one non-limitingexample includes InGaAs) in the gain region. The energy injected intothe gain region resonates between two mirrors prior to emission. Forexample, the light may reflect between two distributed Bragg reflectorsformed from alternating layers of high- and low-refractive index films.In some embodiments, the top and bottom mirrors may be isolated from thegain region by an insulating dielectric layer.

Another embodiment of a surface-emitting laser 202 is shown in FIG. 4.Like FIG. 3, FIG. 4 depicts a VCSEL. However, the laser shown in FIG. 4includes a free-space region between the top and bottom mirrors, aconfiguration sometimes referred to as a vertical external cavitysurface-emitting laser (VECSEL). Because a VECSEL includes a free-spaceregion, the diode may generate a higher power compared to a similarVCSEL.

Turning back to FIG. 1, optical assembly 120 transmits light generatedby light source 118 to illuminate a portion of image environment 106.For purposes of discussion, the lit portion of image environment 106 maybe broken down into an illumination depth region and an illuminationenvelope region. The illumination depth region refers to a depth offocus of the projected light. In the embodiment shown in FIG. 1,illumination light 108 is relayed to an illumination depth region 122bounded by a near edge 124 and a far edge 126. For example, in someembodiments, illumination depth region 122 may be approximately 3.5 mdeep.

The illumination envelope region refers to a cross-sectional area thatis lit with illumination light 108. In the embodiment shown in FIG. 1, arectangularly-shaped illumination envelope region 128 is representedwith horizontal dimension 130 and with vertical dimension 132. However,it will be appreciated that any suitably shaped illumination enveloperegion 128 (e.g., an elliptical shape, a polygon shape, or other closedshape) may be formed without departing from the scope of the presentdisclosure.

As mentioned above, in some embodiments, the lasers included in lightsource 118 may be arranged in a shape that matches that of a desiredemission envelope (e.g., a shape or pattern of light projected by thelasers), and optical assembly 120 may be configured to transmit or relaythat shape to the far field. In such embodiments, the emission envelopeand illumination envelope region 128 may take the shape of thearrangement of the lasers. Thus, as one specific example, arectangularly-shaped array of surface-emitting lasers may be used togenerate a rectangularly-shaped light envelope in the far field. Inother embodiments, optical assembly 120 may be configured re-shape theemission envelope. For example, light emitted from square arrangement ofsurface-emitting lasers may be reshaped into a rectangularly-shapedlight envelope in the far field.

Further, in some embodiments, optical assembly 120 may shape thecross-sectional light intensity/irradiance profile of illumination light108 from a Gaussian profile into a differently-shaped illuminationprofile. For example, in some embodiments, illumination light 108 may beshaped into an illumination profile exhibiting a flat-topped, mesa-likeshape that is symmetrically oriented around an optical axis ofillumination light 108. In such embodiments, the irradiance ofillumination light 108 may have a constant intensity, within anacceptable tolerance, in a region near the optical axis (e.g., a regioncorresponding to a top of the mesa). The irradiance may then decrease inintensity in region farther from the optical axis (e.g., a regioncorresponding to sidewalls of the mesa).

In some other embodiments, illumination light 108 may be characterizedby a cross-sectional light profile that is more intense farther from anoptical axis of illumination light 108 than closer to an optical axis ofthe illumination light. FIG. 5 shows an embodiment of a relationship 500between incoherent irradiance and cross-sectional position within anexample light profile 502 for illumination light. In the example shownin FIG. 5, light profile 502 exhibits a greater irradiant intensity in aregion farther from optical axis 504 than at positions closer to opticalaxis 504. Metaphorically, light profile 502 exhibits cross-sectionalirradiance profile somewhat resembling a capital letter “M” arrangedabout optical axis 504.

Without wishing to be bound by theory, generating an “M”-shaped profilefor the illumination light may offset a “W”-shaped intensity profilereceived at image sensor 110 due to reflection effects caused by objectsin the image environment. In other words, the net effect of supplyinglight with an “M”-shaped profile to image environment 106 may be thatimage sensor 110 detects return light having a mesa-shaped profile.

FIG. 6 schematically shows an embodiment a lens system 600 configured torelay an image of light source 118 into image environment 106. Lenssystem 600 includes a condenser lens stage 602, a relay lens stage 604,and an optional Schmidt plate 606, each of which is described in moredetail below.

FIG. 6 also depicts an example light source 118 comprising three lightemitters. As used herein, a light emitter may comprise one or moresurface-emitting lasers. For example, a single light emitter maycomprise a single VCSEL, a single array of VCSELs (whether distributedin an ordered manner or a random fashion within the array), etc. Lightfrom the three emitters is directed (shown as light paths 608A, 608B,and 608C in FIG. 6) via lens system 600 so that light from each emitteris collimated and then routed to different regions of the far field. Inthis manner, lens system 600 fills illumination envelope region 128 withlight by directing light from each surface-emitting laser element todifferent areas within illumination envelope region 128.

Lens system 600 may utilize a high f-number aperture stop 610 to achievea desired depth of field for the relayed image source light in theillumination depth region 122. In some non-limiting embodiments,f-numbers in a range of f/250 to f/1000 may be used to provide anillumination depth region having a depth of field in a correspondingrange of 500 to 3500 mm.

Condenser lens stage 602 is positioned within lens system 600 to receivelight from light source 118, condensing divergent rays of the emittedlight and forming aperture stop 610. In some embodiments, condenser lensstage 602 may be configured to condense the light received withoutmagnifying or demagnifying the light beyond an acceptable tolerance.Additionally or alternatively, in some embodiments, condenser lens stage602 may be configured to impart or shape the light received into aselected light illumination profile. For example, condenser lens stage602 may distort light received from light source 118 to generate the“M”-shaped profile described above, or any other suitablecross-sectional illumination profile.

Relay lens stage 604 is positioned to receive light from condenser lensstage 602 and relay an image of light source 118 into illumination depthregion 122. Stated differently, relay lens stage 604 provides the powerwithin lens system 600 to transmit the image of light source 118 intoimage environment 106, forming and lighting illumination envelope region128.

In some embodiments, an optional Schmidt plate 606 may be includedwithin lens system 600, positioned at an entrance pupil 612 of lenssystem 600. Schmidt plate 606 may be used to introduce aberrations toillumination light to reduce the intensity of diffraction artifacts thatmay be introduced by surface-emitting lasers 202. Further, Schmidt plate606 may help to achieve a desired light illumination profile. Forexample, including Schmidt plate 606 may emphasize peaks and valleyswithin an “M”-shaped illumination profile imparted by condenser lensstage 602. As the defocusing effect of Schmidt plate 606 may impact thecollimating effect of condenser lens stage 602, potentially reducingdepth of illumination depth region 122, inclusion of Schmidt plate 606may be accompanied by a compensatory adjustment to the f-number of lenssystem 600.

While lens system 600 depicts classical lenses for clarity, it will beappreciated that any suitable embodiment of the lens stages describedabove may be included within lens system 600 without departing from thescope of the present disclosure. For example, in some embodiments,wafer-level optics may be employed for one or more of the lens stages.As used herein, a wafer optic structure refers to an optical structureformed using suitable formation and/or patterning processes like thoseused in semiconductor patterning. Wafer-level optics may offer thepotential advantage of cost-effective miniaturization of one or more ofthe lens stages and/or enhance manufacturing tolerances for such stages.

FIG. 7 schematically shows another embodiment of an example lens system700 for illuminator 102. In the embodiment shown in FIG. 7, wafer opticelement 702 encodes a prescription for a portion of a condenser lensstage on a light receiving surface 704 and a prescription for a relaylens stage on light emitting surface 706. Wafer optic element 708encodes a prescription for a Schmidt plate on light receiving surface710. In the example shown in FIG. 7, the light distributed by lenssystem 700 is less collimated relative to the light distributed by theembodiment of lens system 600 shown in FIG. 6, leading to overlap of thelight paths 712A, 712B, and 712C in the far field.

While lower levels of collimation may spread illumination light 108 overa greater area, that spreading be accompanied by a reduction inillumination depth region 122. Accordingly, in some embodiments, a lenssystem may be formed using diffractive optics. If diffractive opticalelements are employed for one or more of the lens elements/stagesincluded in the lens system, a diffractive optic substrate will have aprescription for those stages encoded on a respective surface of thesubstrate. In some embodiments, for example, a single substrate may havea light receiving surface that encodes a prescription for one lens stageand a light emitting surface that encodes a prescription for anotherlens stage. Because the working surface of a diffractive optic iscomparatively thinner than a classical lens analog, which may have athickness set by a radius of curvature for the classical lens, thediffractive optic may offer similar potential miniaturizationenhancements to wafer optics, but may also preserve collimation anddepth of field. Moreover, in some embodiments, diffractive optics maypermit one or more optical elements to be removed.

FIG. 8 schematically shows another embodiment of a lens system 800suitable for use with illuminator 102. In the embodiment shown in FIG.8, diffractive optic element 802 encodes a prescription for a condenserlens stage on a light receiving surface 804 and a prescription for arelay lens stage on light emitting surface 806. A Schmidt plate is notincluded in the example illuminator 102 shown in FIG. 8. In the exampleshown in FIG. 8, the light distributed by lens system 800 may be morehighly collimated relative to the light distributed by the embodiment oflens system 600 shown in FIG. 6.

It will be appreciated that the relative positions of the optical stagesdescribed above may be varied in any suitable manner without departingfrom the scope of the present disclosure. For example, in someembodiments, one or more of the optical stages may be varied to increasethe apparent size of light source 118. Increasing the size of lightsource 118 may reduce a user's ability to focus on the light source(e.g., by making the light source appear more diffuse) and/or may avoiddirectly imaging light source 118 on a user's retina. As a non-limitingexample, some systems may be configured so that an image of light source118 may not be focused on a user's retina when the user's retina ispositioned within 100 mm of light source 118.

In some embodiments, increasing the apparent source size may includepositioning relay lens stage 604 closer to light source 118, which maycause illumination light 108 to diverge faster, depending upon theconfiguration of the relay lens stage 604 and light source 118. Becausethis adjustment may also lead to an increase in the field of view and adecrease in illumination depth region 122, a prescription and/orposition for condenser lens stage 602 may also be adjusted to adjust thefocal length of optical assembly 120 while the arrangement and pitch ofsurface-emitting lasers 202 included within light source 118 may bevaried to adjust illumination envelope region 128. In some embodiments,optical assembly 120 may also be configured to transform the emissionenvelope into a different shape while relaying the light to imageenvironment 106.

FIG. 9 schematically shows a sectional view of another embodiment of anilluminator 102 in the form of a homogenizing light guide 902.Homogenizing light guide 902 is configured to increase an apparent sizeof light source 118 by receiving light from light source 118 via lightreceiving surface 904 and spreading it within the light guide. In someembodiments, light source 118 may include an array of surface-emittinglasers 202, and/or may include any other suitable light emittingdevices. In one specific example, light source 118 may include a long,thin, array of surface-emitting lasers 202.

Homogenizing light guide 902 takes the form of an optical wedge, thoughit will be appreciated that any suitable light guide configured tospread and smooth light may be employed without departing from thepresent disclosure. In the embodiment shown in FIG. 9, light is retainedwithin homogenizing light guide 902 via total internal reflection intotal reflection region 906. Upon leaving total reflection region 906,light encounters a light exit region 908 where the opposing faces of thewedge are angled with respect to light emission surface 910, whichallows light to exceed the critical angle for total internal reflectionrelative to light emission surface 910, and thereby escape the opticalwedge.

Light passing along homogenizing light guide 902 may travel in acollimated or near-collimated path to light emission surface 910. Insome non-limiting examples, light may fan out by 9 degrees or less whiletraveling between light receiving surface 904 and light emission surface910. However, light from light source 118 may blend and mingle whiletraveling through homogenizing light guide 902, so that the lightemitted at light emission surface 910 causes the plurality of lasers toappear as a single, larger source located at light emission surface 910.

After emission from light emission surface 910, the light is received bya microlens array 912 and spread to fill illumination envelope region128. Microlens array 912 includes a plurality of small lens elementsconfigured to diverge the light and projected it into image environment106. For example, FIG. 10 schematically shows a front view of a portionof an example microlens array 912 including a plurality of lens elements1002 retained by a frame 1004. As shown in FIG. 10, each lens element1002 is defined with reference to a long-axis lens element pitch 1006that is different from a short-axis lens element pitch 1008, so thateach lens element 1002 has an oblong shape. In the embodiment shown inFIG. 10, the pitch is defined with reference to the center of each cell,which may correspond to an apex of each lens surface. Other suitablepitch definitions may be employed in other embodiments without departingfrom the scope of the present disclosure.

Each of the lens elements 1002 included in microlens array 912 isconfigured to create the desired angular field of illumination foroptical assembly 120. Put another way, each lens element 1002 isconfigured to impart a selected angular divergence to incoming light. Asused herein, divergent light refers to coherent light that is spreadfrom a more collimated beam into a less collimated beam. Divergent lightmay have any suitable illumination intensity cross-section, as explainedin more detail below, and may have any suitable divergence angle, asmeasured between an optical axis and an extreme ray of the divergentlight. The divergence angle may adjusted by adjusting the pitch of thelens elements 1002 within microlens array 912. By spreading the incominglight, microlens array 912 transmits light to all regions withinillumination envelope region 128.

FIG. 11 schematically shows a perspective of an embodiment of anindividual lens element 1002 having a convex lens surface 1102. Lenssurface 1102 is shaped in part by pitch dimensions for lens element 1002(e.g., cell dimensions for lens element 1002). In turn, the pitchdimensions for the cell may affect the aspheric nature of lens surface1102. Consequently, the diverging power of lens element 1002 isestablished at least in part by the pitch dimensions. In the embodimentshown in FIG. 11, where lens element 1002 is depicted as having anoblong cell shape, convex lens surface 1102 will have a first divergenceangle 1104, defined between optical axis 1106 and extreme ray 1108, thatwill be different from a second divergence angle 1110, defined betweenoptical axis 1106 and extreme ray 1112. When projected into imageenvironment 106, the illumination light, spread in respective directionsaccording to these divergence angles, will in turn establish theboundaries for illumination envelope region 128.

In some embodiments, the degree of divergence that may be realized bylens elements 1002 may be affected by the refractive index of thematerial from which the lenses are formed. As the lens curvatureincreases, the light approaches a total internal reflection limit.However, by increasing the index of refraction, a selected divergenceangle may be achieved with comparatively less light bending. Forexample, in some embodiments, lens elements 1002 may be made fromoptical grade poly(methyl methacrylate) (PMMA), which has a refractiveindex of approximately 1.49. In other embodiments, lens elements 1002may be made from optical grade polycarbonate (PC), having a refractiveindex of approximately 1.6. Lens elements 1002 made from PC may haveless curvature to obtain the same divergence angle compared to elementsmade from PMMA. It will be appreciated that any suitable optical gradematerial may be used to make lens elements 1002, including the polymersdescribed above, optical grade glasses, etc.

While the embodiment of microlens array 912 shown in FIG. 10 depictsconvex lens surfaces included in the array to be facing away from lightemission surface 910, in some embodiments, convex lens surface 1102 maybe positioned toward light source 118. Positioning convex lens surface1102 to face light source 118 may result in comparatively higher anglesof incidence before the light experiences total internal reflectionwithin the lens element relative to examples where lens surface 1102faces away from light source 118. In turn, the angular field ofillumination, and thus the illumination envelope region, may be largerwhen lens surface 1102 faces light source 118. Further, positioning lenssurface 1102 to face light source 118 may reduce or eliminate somesurface coatings (e.g., anti-reflective coatings such as MgF₂) that mayotherwise be applied if lens surface 1102 faces in another direction.

The aggregate effect of spreading the coherent light at each lenselement 1002 may be to shape the cross-sectional lightintensity/irradiance profile from a Gaussian profile associated withincident coherent light into a differently-shaped illumination profile.For example, in some embodiments, as few as six lens elements 1002 maybe sufficient to form a desired illumination profile such as the“M”-shaped illumination profile described above.

FIG. 12 schematically shows another embodiment of illuminator 102 thatincludes a homogenizing light guide 1202 that has the form of a slab,rather than a wedge. Homogenizing light guide 1202 is configured toreceive light from light source 118 via light receiving surface 1204.Light reflects off of a total internal reflection surface 1206 and isdirected toward a light emission region 1208 where some of the light isemitted via light emission surface 1210. Light emission surface 1210 isconfigured as a partial internal reflection surface, reflecting aportion of the light toward total internal reflection surface 1206 forcontinued propagation while allowing another portion to escape. In somenon-limiting examples, light emission surface 1210 may be configured toreflect approximately 95% of incident light at any individual reflectioninstance, allowing 5% to be emitted to microlens array 912. Thereflected light may re-encounter light emission surface 1210 and againexperience partial emission of the incident light. Such partial emissioninstances may be repeated until substantially all of the light receivedby homogenizing light guide 1202 is emitted via light emission surface1210. In some embodiments, homogenizing light guide 1202 may include atotal internal reflection region positioned opposite total internalreflection surface 1206 to conserve and propagate received light untilit reaches light emission region 1208.

Yet another approach to reshaping the emission envelope and increasingthe apparent source size includes the use of a folded optical pathwithin optical assembly 120. FIG. 13 schematically shows anotherembodiment of illuminator 102. The embodiment shown in FIG. 13 alsodepicts a cross-section of a reflective light guide 1302 that receivesat least a portion of the light from light source 118 and emits thelight received to microlens array 912. The light follows a folded lightpath (shown as light paths 1304A, 1304B, and 1304C in FIG. 13) whiletransiting reflective light guide 1302. The folded light path shown inFIG. 13 includes complementary angles that allow total internalreflection within reflective light guide 1302. The use of complementaryangles within reflective light guide 1302 may provide self-correction ofone or more reflection errors caused by misplacement of the light guide.It will be appreciated that in some embodiments, a folded light path mayinclude one or more mirrors suitably positioned to achieve the desiredoptical path.

In the example shown in FIG. 13, errors that may be introduced byhorizontally misplacing reflective light guide 1302 may be canceled byreflection through these complementary angles. For example, lighttraveling along light path 1304B is received at light entrance 1306 andstrikes a first total internal reflection surface 1308, where it isreflected at a first angle 1312 toward a second total internalreflection surface 1310. At second total internal reflection surface1310, the light is reflected at a second angle 1314 toward lightemission surface 1316. The total internal reflection surfaces arearranged with respect to each other so that angle 1312 is complementarywith angle 1314, so no angular error exists within the light exitinglight emission surface 1316. Thus, potential manufacturing errors orimpacts to optical assembly 120 may be self-correcting within anacceptable tolerance.

FIG. 14 shows a flowchart depicting an embodiment of a method 1400 ofprojecting illumination light into an image environment. It will beappreciated that method 1400 may be performed by any suitable hardware,including but not limited to the hardware described herein. Further, itwill be appreciated that the embodiment of method 1400 shown in FIG. 14and described below is presented for the purpose of example. In someembodiments, any of the processes described with reference to FIG. 14may be supplemented with other suitable processes, omitted, and/orsuitably reordered without departing from the scope of the presentdisclosure.

At 1402, method 1400 includes generating coherent light using aplurality of surface-emitting lasers. For example, coherent visible,infrared, or near-infrared light may be generated using suitablesurface-emitting lasers like the VCSELs and/or VECSELs described herein.

In some embodiments, method 1400 may include homogenizing the coherentlight at 1404. Homogenizing the coherent light may increase the apparentsize of the light source and/or may cause the plurality ofsurface-emitting lasers to appear as a single source. In some of suchembodiments, homogenizing the coherent light at 1404 may include, at1406, homogenizing the illumination light using a homogenizing lightguide. Non-limiting examples of homogenizing light guides includehomogenizing light wedges and homogenizing light slabs configured toemit light along one surface via partial reflection of the light whiletotally reflecting light from another surface within the light guide. Inother embodiments, homogenizing the coherent light at 1404 may include,at 1408, homogenizing the illumination light using a reflective lightguide. Non-limiting examples of reflective light guides include guidesthat define folded light paths. In yet other embodiments, suchhomogenization may be omitted.

At 1410, method 1400 includes relaying the illumination light to theimage environment. In some embodiments, relaying the illumination lightto the image environment may include, at 1412, relaying an image of thelight source to the image environment via a lens system In some of suchembodiments, the apparent size of the image source may be adjusted byadjusting the focal length, illumination depth region, and illuminationenvelope region of the lens system.

In some embodiments, relaying the illumination light to the imageenvironment at 1410 may include, at 1414, relaying collimated light tothe image environment. For example, as described above, light from eachlaser of an array of surface-emitting laser may be collimated, and thendirected in a different direction than collimated light from otherlasers in the array. As another example, a microlens array may be usedto relay the light received from a suitable homogenizing light guide todifferent portions of the illumination envelope region.

In some embodiments, the methods and processes described above may betied to a computing system of one or more computing devices. Inparticular, such methods and processes may be implemented as acomputer-application program or service, an application-programminginterface (API), a library, and/or other computer-program product.

TOF depth camera 100 shown in FIG. 1 depicts an example of anon-limiting embodiment of a computing system that may perform one ormore of the methods and processes described above. For example, in theembodiment shown in FIG. 1, light generation module 150 may includeinstructions executable to operate illuminator 102, and depthinformation module 152 may include instructions executable to operateimage sensor 110 and interpret image information detected by detector114. While the modules shown in FIG. 1 are illustrated as distinct,standalone entities within TOF depth camera 100, it will be appreciatedthat the functions performed by such modules may be integrated and/ordistributed throughout TOF depth camera 100 and/or a computing deviceconnected locally or remotely with TOF depth camera 100 withoutdeparting from the scope of the present disclosure.

TOF depth camera 100 includes a logic subsystem 160 and a storagesubsystem 162. TOF depth camera 100 may optionally include a displaysubsystem 164, input/output-device subsystem 166, and/or othercomponents not shown in FIG. 1.

Logic subsystem 160 includes one or more physical devices configured toexecute instructions. For example, logic subsystem 160 may be configuredto execute instructions that are part of one or more applications,services, programs, routines, libraries, objects, components, datastructures, or other logical constructs. Such instructions may beimplemented to perform a task, implement a data type, transform thestate of one or more components, or otherwise arrive at a desiredresult.

Logic subsystem 160 may include one or more processors configured toexecute software instructions. Additionally or alternatively, logicsubsystem 160 may include one or more hardware or firmware logicmachines configured to execute hardware or firmware instructions. Theprocessors of logic subsystem 160 may be single-core or multi-core, andthe programs executed thereon may be configured for sequential, parallelor distributed processing. Logic subsystem 160 may optionally includeindividual components that are distributed among two or more devices,which can be remotely located and/or configured for coordinatedprocessing. Aspects of the logic subsystem may be virtualized andexecuted by remotely accessible networked computing devices configuredin a cloud-computing configuration.

Storage subsystem 162 includes one or more physical, non-transitory,devices configured to hold data and/or instructions executable by logicsubsystem 160 to implement the herein-described methods and processes.When such methods and processes are implemented, the state of storagesubsystem 162 may be transformed—e.g., to hold different data.

Storage subsystem 162 may include removable media and/or built-indevices. Storage subsystem 162 may include optical memory devices (e.g.,CD, DVD, HD-DVD, Blu-Ray Disc, etc.), semiconductor memory devices(e.g., RAM, EPROM, EEPROM, etc.) and/or magnetic memory devices (e.g.,hard-disk drive, floppy-disk drive, tape drive, MRAM, etc.), amongothers. Storage subsystem 162 may include volatile, nonvolatile,dynamic, static, read/write, read-only, random-access,sequential-access, location-addressable, file-addressable, and/orcontent-addressable devices. In some embodiments, logic subsystem 160and storage subsystem 162 may be integrated into one or more unitarydevices, such as an application-specific integrated circuit (ASIC), or asystem-on-a-chip.

It will be appreciated that storage subsystem 162 includes one or morephysical, non-transitory devices. However, in some embodiments, aspectsof the instructions described herein may be propagated in a transitoryfashion by a pure signal (e.g., an electromagnetic signal, an opticalsignal, etc.) that is not held by a physical device for a finiteduration. Furthermore, data and/or other forms of information pertainingto the present disclosure may be propagated by a pure signal.

The terms “module” and “program” may be used to describe an aspect ofthe computing system implemented to perform a particular function. Insome cases, a module or program may be instantiated via logic subsystem160 executing instructions held by storage subsystem 162. It will beunderstood that different modules and/or programs may be instantiatedfrom the same application, service, code block, object, library,routine, API, function, etc. Likewise, the same module, and/or programmay be instantiated by different applications, services, code blocks,objects, routines, APIs, functions, etc. The terms “module” and“program” may encompass individual or groups of executable files, datafiles, libraries, drivers, scripts, database records, etc.

When included, display subsystem 164 may be used to present a visualrepresentation of data held by storage subsystem 162. This visualrepresentation may take the form of a graphical user interface (GUI). Asthe herein described methods and processes change the data held by thestorage subsystem, and thus transform the state of the storagesubsystem, the state of display subsystem 164 may likewise betransformed to visually represent changes in the underlying data.Display subsystem 164 may include one or more display devices utilizingvirtually any type of technology. Such display devices may be combinedwith logic subsystem 160 and/or storage subsystem 162 in a sharedenclosure, or such display devices may be peripheral display devices.

When included, input/output-device subsystem 166 may be configured tocommunicatively couple the computing system with one or more othercomputing devices. Input/output-device subsystem 166 may include wiredand/or wireless communication devices compatible with one or moredifferent communication protocols. As non-limiting examples,input/output-device subsystem 166 may be configured for communicationvia a wireless telephone network, or a wired or wireless local- orwide-area network. In some embodiments, input/output-device subsystem166 may allow the computing system to send and/or receive messages toand/or from other devices via a network such as the Internet.Input/output-device subsystem 166 may also optionally include orinterface with one or more user-input devices such as a keyboard, mouse,game controller, camera, microphone, and/or touch screen, for example.

It will be understood that the configurations and/or approachesdescribed herein are exemplary in nature, and that these specificembodiments or examples are not to be considered in a limiting sense,because numerous variations are possible. The specific routines ormethods described herein may represent one or more of any number ofprocessing strategies. As such, various acts illustrated and/ordescribed may be performed in the sequence illustrated and/or described,in other sequences, in parallel, or omitted. Likewise, the order of theabove-described processes may be changed.

The subject matter of the present disclosure includes all novel andnonobvious combinations and subcombinations of the various processes,systems and configurations, and other features, functions, acts, and/orproperties disclosed herein, as well as any and all equivalents thereof.

The invention claimed is:
 1. A time-of-flight depth camera configured tocollect image data from an image environment illuminated by illuminationlight, the time-of-flight depth camera comprising: a light sourceincluding a plurality of surface-emitting lasers configured to generatecoherent light, the light source comprising an arrangement of theplurality of surface-emitting lasers in a rectangular shape; a lenssystem configured to project an image of the light source to the imageenvironment by transmitting collimated light emitted from a firstsurface-emitting laser to the image environment in a different directionthan collimated light emitted from a second surface-emitting laser, thelens system comprising: a first stage positioned to condense lightreceived from the light source, and a second stage positioned to receivelight from the first stage, the second stage being configured to relaythe image of the light source into the image environment to illuminatethe image environment; and an image sensor configured to detect at leasta portion of return light reflected from the image environment.
 2. Thetime-of-flight depth camera of claim 1, where at least one of theplurality of surface-emitting lasers is selected from the groupconsisting of vertical external cavity surface-emitting lasers (VECSELs)and vertical-cavity surface-emitting lasers (VCSELs).
 3. Thetime-of-flight depth camera of claim 1, where the lens system has anf-number configured to provide an illumination depth region of at least0.5 m.
 4. The time-of-flight depth camera of claim 1, further comprisinga Schmidt plate positioned at an entrance pupil of the lens system. 5.The time-of-flight depth camera of claim 1, where each of the pluralityof surface-emitting lasers generates coherent light having an angulardivergence.
 6. The time-of-flight depth camera of claim 1, where thelens system includes a single substrate having a light receiving surfaceconfigured to receive light from the light source and a light emittingsurface configured to transmit light to the image environment, where thelight receiving surface includes a first pattern encoding a firstprescription for the first stage, and where the light emitting surfaceincludes a second pattern encoding a second prescription for the secondstage.
 7. The time-of-flight depth camera of claim 1, where the firststage is further configured to shape the coherent light into lighthaving a light profile that is more intense at a location farther froman optical axis of the light than at a location closer to the opticalaxis of the light.